What are the most unreliable car brands? - Which?

From extended periods off the road for repairs to high breakdown and fault rates, these are the car brands that fared the worst in our latest reliability survey. Our robust reliability research is powered by the experiences of 63,334 owners who have given detailed insight into the ownership and maintenance of 72,470 cars (Which? car survey, in field April 2025 to June 2025). The reliability scores are calculated from data including the number of breakdowns and faults suffered by cars in the past 12 months. Faults are weighted according to seriousness. So the more severe the fault and the more time the car is off the road, the harder the model will be hit in our results. These scores are represented by a star rating, with one star being the worst and five the best.